1. Field of the Invention
The invention relates to a strain measurement apparatus, a linear expansion coefficient measurement method, and a correction coefficient measurement method for a temperature distribution detector.
2. Description of Related Art
With regard to component parts, such as an exhaust manifold or the like, of an exhaust system of an engine mounted on a vehicle, it is known that since the exhaust gas discharged from the engine has high temperature, thermal strain causes stress to occur, which affects the service life length. In order to evaluate the service life length of exhaust-system component parts of an engine, it is necessary to measure strain. To that end, various arts for measuring three-dimensional configurations have been proposed.
For example, there is disclosed a three-dimensional configuration measurement apparatus that measures a three-dimensional configuration of a measurement object by projecting a pattern onto the measurement object disposed in a picture-taking region of two cameras and acquiring stereo images of the measurement object with the projected pattern, and performing a stereo image processing of the acquired images (see Japanese Patent Application Publication No. 2009-270915 (JP 2009-270915 A)).
However, although the three-dimensional configuration measurement apparatus described in JP 2009-270915 A is capable of measuring the strain of a measurement object, the apparatus is not capable of finding the stress caused by thermal strain. That is, even when an exhaust system component part of an engine has a high temperature, the aforementioned stress does not occur if the exhaust system component part is allowed to freely expand, but the aforementioned stress occurs when the exhaust system component part is subjected to external constraint as is the case with a part connected to the engine, for example, and there is a temperature distribution in an engine exhaust system component part or the like.
That is, the above-described three-dimensional configuration measurement apparatus is not capable of measuring the strain that corresponds to the aforementioned stress (the stress caused by thermal strain) that affects the service life of a measurement object.